What is earthing type of earthing different type of earthing system

Introduction '

 In power system , * grounding or earthing means connecting frame of electrical equipment ( non - current carrying part ) or some electrical part of the system ( e.g , neutral point in a star - connected system , one conductor of the secondary of a transformer etc. ) to earth i.e. soil . This connection to earth may be through a conductor or some other circuit element ( e.g. a resistor , a circuit breaker etc. ) depending upon the situation . Regardless of the method of connection to earth , grounding or earthing offers two principal advantages . First , it provides protection to the power system . For example , if the neutral point of a star - connected system is grounded through a circuit breaker and phase to earth fault occurs on any one line , a large fault current will flow through the circuit breaker . Thecircuit breaker will open to isolate the faulty line . This protects the power system from the harmful effects of the fault . Secondly , earthing of electrical equipment ( e.g. domestic appliances , hand - held tools , industrial motors etc. ) ensures the safety of the persons handling the equipment . For example , if insulation fails , there will be a direct contact of the live conductor with the metallic part ( i.e. frame ) of the equipment . Any person in contact with the metallic part of this equipment will be subjected to a dangerous electrical shock which can be fatal . In this chapter , we shall discuss the importance of grounding or earthing in the line of power system with special emphasis on neutral grounding .

 

 

Grounding or Earthing

 The process of connecting the metallic frame ( i.e. non - current carrying part ) of electrical equip ment or some electrical part of the system ( e.g. neutral point in a star - connected system , one con ductor of the secondary of a transformer etc. ) to earth ( i.e. soil ) is called grounding or earthing . It is strange but true that grounding of electrical systems is less understood aspect of power system . Nevertheless , it is a very important subject . If grounding is done systematically in the line of the power system , we can effectively prevent accidents and damage to the equipment of the power system and at the same time continuity of supply can be maintained . Grounding or earthing may be classified as : ( i ) Equipment grounding ( ii ) System grounding . Equipment grounding deals with earthing the non - current - carrying metal parts of the electrical equipment . On the other hand , system grounding means earthing some part of the electrical system e.g. earthing of neutral point of star - connected system in generating stations and sub - stations .

 

Type of Grounding

 

Equipment Grounding

 

The process of connecting non - current - carrying metal parts ( i.e. metallic enclosure ) of the electri cal equipment to earth ( i.e. soil ) in such a way that in case of insulation failure , the enclosure effectively remains at earth potential is called equipment grounding . 

 

 

System Grounding

The process of connecting some electrical part of the power system (e.g. neutral point of a star connected system, one conductor of the secondary of a transformer etc. ) to earth ( i.e. soil ) is called system grounding . The system grounding has assumed considerable importance in the fast expanding power system. By adopting proper schemes of system grounding, we can achieve many advantages including protection, reliability and safety to the power system network. But before discussing the various aspects of neutral grounding, it is desirable to give two examples to appreciate the need of system grounding.

 

 

Neutral Grounding

 

The process of connecting neutral point of 3 - phase system to earth ( i.e. soil ) either directly or through some circuit element ( e.g. resistance , reactance etc. ) is called neutral grounding . Neutral grounding provides protection to personal and equipment . It is because during earth fault , the current path is completed through the earthed neutral and the protective devices ( e.g. a fuse etc. ) operate to isolate the faulty conductor from the rest of the system . This point is illustrated in

 

 

Solid Grounding

 When the neutral point of a 3 - phase system ( e.g. 3 phase generator , 3 - phase transformer etc. ) is directly * connected to earth ( i.e. soil ) through a wire of neg ligible resistance and reactance , it is called solid grounding or effective grounding .

 

Resistance Grounding

 

In order to limit the magnitude of earth fault current , it is a common practice to connect the neutral point of a 3 - phase system to earth through a resistor . This is called resistance grounding . When the neutral point of a 3 - phase system ( e.g. 3 - phase generator , 3 - phase transformer etc. ) is connected to earth ( i.e. soil ) through a resistor , it is called resistance grounding .